This invention relates generally to a process and apparatus for the selective production of hot water and steam from a volume of water pumped toward a constantly operating heater. More particularly, the process and apparatus of the invention include an actuator on a steam collector used for the production of steam suitable for the heating of drinks. Insertion of the steam collector into the apparatus causes a decrease in pumping frequency and a temperature level increase in the heater.
Espresso coffee machines normally permit water to be heated to about 96.degree. C. and forced at a suitable pressure through the ground coffee in order to obtain an extract known as espresso coffee. Machines of this type normally have a water tank, an electrically heated constantly operated heater, and a pressure pump located between the tank and heater for pumping the super heated water through a conduit toward the heater. The pump may be of a swing-lever type, for example, wherein a lifting member thereof is magnetically shifted forward and returned under the action of a spring for effectively pressurizing the heated water.
Coffee machines of this type have also been provided with a steam producing capability for the heating of drinks so as to, for example, heat milk by passing a jet of steam therethrough. Thus, a strainer holder normally provided for the brewing of the coffee is interchangeable with some type of steam collector when steam is to be produced.
For the production of steam, a much smaller volume of water per unit of time must be pumped toward the heater for heating the water so that the water will completely evaporate in the heater to avoid any mixture of hot water and steam being collected by the steam collector. Such a mixture is undesirable since the drink to be heated would become watered down. Since the water must completely evaporate in the heater, the discharge volume of the pressure pump must be reduced. In the prior art machines, this reduction of discharge volume of the pump has been achieved by shortening the stroke of the pump which, if operating with AC current, may be carried out by shift control. However, with the pump operating at such short strokes it has been difficult to precisely regulate complete evaporation of the conveyed volume of water in the heater. Thus, with the pump conveying more than the desired amount of water, steam mixed with water emerges from the machine at a time when only steam is preferred.
Moreover, drinks intended to be steam heated have been known to be also watered down by hot water due to some improper manipulation of the machine by the operator even through the machine is otherwise capable of producing the desired steam. Such a faulty manipulation has been known to occur because of the steam and hot water production switches being made to operate independently of one another. Thus, whenever it is possible to operate the switch for the production of steam when a strainer containing coffee is inserted into the machine for the production of coffee, the coffee is contaminated with the steam and becomes undrinkable. On the other hand, when the switch for the production of hot water may be operated at a time when it is desired to heat a drink upon insertion of a steam collector into the machine, the drink to be heated will obviously become watered down.